3 How many moles of hydrogen is present in 386 mL of H colle

3. How many moles of hydrogen is present in 38.6 mL of H, collected over water at 250 C andataprs sure of 748 torr?

Answer :- n = 0.00151 mole of H2

The vapor pressure of the water in the collecting vessel is 23.8 torr

Since the total pressure is the atmospheric pressure

The pressure due to the hydrogen is,

748.0 - 23.8 = 724.2 torr

Since you are given volume, pressure, and temperature, you can use the ideal gas law

PV = nRT

Where,

P = the pressure

V = the volume

n = the number of moles

R = the universal gas constant

T = the temperature

to solve for n, the number of moles of gas.

The universal gas constant, R, is usually given as

R=0.082atmL / molK

Which means that you will have to convert the pressure of the gas from torr to atm by using the conversion factor

1 atm = 760 torr

So, plug in your values and solve for n

n = PV / RT

n = ((724.2/760) × 0.0386L) / (( 0.082atm.L/ mol.k)(273 + 25)

n = 0.00151 mole of H2